Combine the flour, sugar and baking powder in the bowl of a stand mixer or handheld electric mixer. Beat on low speed just to blend. Add the chilled butter; beat on low speed for 4 or 5 minutes, until the mixture starts to look crumbly with some large chunks. Stop to scrape down the bowl.

Add the currants, if using; beat on low speed until evenly distributed.

Pour in the milk and heavy cream; beat on low speed for several seconds, just until the liquids are incorporated, to form a soft dough.

Lightly flour a work surface. Transfer the dough there and pat it to an even thickness of about 1 inch. Cover loosely with a clean kitchen towel; let it rest for 30 minutes.

Preheat the oven to 400 degrees. Line a baking sheet with parchment paper or a silicone liner.

Flour the edges of your biscuit cutter, then use it to cut out 17 to 20 scones (straight down, without twisting), arranging them at least 1 inch apart on the baking sheet as you work and re-flouring the cutter each time. Try to reroll the scraps no more than once as the subsequent portions of dough may not rise as much in the oven.

Brush the tops of the scones with milk. Bake (middle rack) for about 16 minutes, turning the sheet from front to back halfway through, until lightly golden.

Transfer them to a wire rack to cool for a few minutes before serving, or cool completely before storing.